What is the difference between php7 and php5 syntax

The syntax differences between php7 and php5 are: 1. PHP7 introduces strict type declaration, while the type of PHP5 variables is implicit; 2. PHP7 introduces support for scalar type declaration, but PHP5 does not; 3. PHP7 introduced the NULL coalescing operator, but PHP5 checks whether a variable exists and is not null, and you need to use a conditional statement; 4. PHP7 added a new comparison operator "<=>", but PHP5 does not; 5. PHP7 introduces new features anonymous classes, but PHP5 does not.

The operating environment of this tutorial: windows10 system, php8.1.3 version, DELL G3 computer.

PHP is a widely used server-side scripting language for developing dynamic websites and web applications. Since PHP7 was released, it has brought some major improvements and new features. This article will focus on the syntax differences between PHP7 and PHP5.

1. Type declaration

PHP7 introduces strict type declaration, which is one of the most obvious differences from PHP5. In PHP5, the type of variables is implicit and developers can directly manipulate variables without making any type declaration. This leads to potential type mismatches and errors.

In PHP7, three different type declarations can be used: mandatory, loose and none. Forced type declarations require that the types of parameters and return values match exactly, otherwise a fatal error will be thrown. Loose type declarations allow some implicit type conversions. An untyped declaration means no type checking is done.

Example:

PHP5:

functionadd($a,$b){ return$a+$b; } PHP7： functionadd(int$a,int$b):int{ return$a+$b; }

2. Scalar type declaration

In PHP7, in addition to supporting traditional type declarations Additionally, support for scalar type declarations has been introduced. Scalar types refer to strings, integers, floating point numbers, and Boolean values.

Example:

functionadd(int$a,float$b):float{ return$a+$b; }

In this way, if a parameter of non-integer or non-floating point type is passed in, a type error will be thrown.

3. NULL coalescing operator

In PHP5, if you want to check whether a variable exists and is not null, you often need to use conditional statements. In PHP7, a new operator "??" is introduced, which is the NULL coalescing operator.

Example:

$name=$_GET['name']??'Guest'; //等效于 $name=isset($_GET['name'])?$_GET['name']:'Guest';

In this way, if the name parameter is not passed in the GET request, $name will be assigned the value 'Guest'.

4. Comparison operator

In PHP7, a new comparison operator "<=>" is added. It returns an integer value representing the relationship between two values. If the left operand is less than the right operand, it returns -1; if the left operand is equal to the right operand, it returns 0; if the left operand is greater than the right operand, it returns 1.

Example:

$a=5; $b=10; $result=$a<=>$b; //$result的值为-1

5. Anonymous class

Anonymous class is a new feature introduced in PHP7, which allows you to define an anonymous class in the code without explicit Type name of the class. This is useful in certain situations, such as when you need to create a simple class temporarily or for a callback function.

Example:

$greeting=newclass{ publicfunctionsayHello(){ echo"Hello,world!"; } }; $greeting->sayHello();

The above are some syntax differences between PHP7 and PHP5. The introduction of PHP7 brought many improvements and new features, including type declarations, NULL coalescing operators, and anonymous classes. These improvements not only improve code readability and maintainability, but also increase program performance and security. If you are using PHP5, consider upgrading to PHP7 to enjoy these benefits .

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